The present invention relates generally to ophthalmic lenses, and more particularly to ophthalmic lenses that provide an enhanced depth of field.
A variety of ophthalmic lenses are employed for correcting visual disorders, such as, cataract, myopia, hyperopia or astigmatism. For example, an intra-ocular lens (IOL) can be implanted in a patient's eye during cataract surgery to compensate for the lost optical power of the removed lens. In many cases, however, the implanted lens may not provide the best focus at the targeted object distance. Some studies have reported that refractive errors as large as 0.5 Diopters can occur in about fifty percent of patients who receive IOLs. Such errors can be caused, for example, by inherent variability associated with calculation methods utilized to choose an IOL's refractive power, inaccuracies in preoperative biometry data, or variations in the IOL's axial placement, tilt or decentration.
A variety of ophthalmic monofocal, bifocal, and multi-focal lenses are known in the art that can be employed, among other applications, to ameliorate the above problems associated with IOLs. Examples of such ophthalmic lenses can include zonal refractive lenses, in which different zones of the lens exhibit different optical powers, and diffractive lenses, in which different diffraction orders are utilized to obtain multi-focal behavior. Such conventional ophthalmic lenses suffer from a number of shortcomings. For example, errors in axial placement of conventional monofocal lenses can significantly degrade their performance.
Accordingly, there is a need for improved monofocal ophthalmic lenses for visual correction that are less prone to refractive errors due to design or positioning factors.